Re: [RFC PATCH 6/9] memory: apple: Add apple-mcc driver to manage MCC perf in Apple SoCs

[Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>]

On 11/10/2021 18:57, Hector Martin wrote:
> This driver binds to the memory controller hardware in Apple SoCs such
> as the Apple M1, and provides a power domain that downstream devices can
> use to change the performance state of the memory controller.
> 
> Signed-off-by: Hector Martin <marcan@marcan.st>
> ---
>  drivers/memory/Kconfig     |   9 +++
>  drivers/memory/Makefile    |   1 +
>  drivers/memory/apple-mcc.c | 130 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 140 insertions(+)
>  create mode 100644 drivers/memory/apple-mcc.c
> 
> diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
> index 72c0df129d5c..48ef3d563a1c 100644
> --- a/drivers/memory/Kconfig
> +++ b/drivers/memory/Kconfig
> @@ -30,6 +30,15 @@ config ARM_PL172_MPMC
>  	  If you have an embedded system with an AMBA bus and a PL172
>  	  controller, say Y or M here.
>  
> +config APPLE_MCC
> +	tristate "Apple SoC MCC driver"
> +	default y if ARCH_APPLE
> +	select PM_GENERIC_DOMAINS
> +	depends on ARCH_APPLE || COMPILE_TEST
> +	help
> +	  This driver manages performance tuning for the memory controller in
> +	  Apple SoCs, such as the Apple M1.
> +
>  config ATMEL_SDRAMC
>  	bool "Atmel (Multi-port DDR-)SDRAM Controller"
>  	default y if ARCH_AT91
> diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
> index bc7663ed1c25..947840cbd2d4 100644
> --- a/drivers/memory/Makefile
> +++ b/drivers/memory/Makefile
> @@ -8,6 +8,7 @@ ifeq ($(CONFIG_DDR),y)
>  obj-$(CONFIG_OF)		+= of_memory.o
>  endif
>  obj-$(CONFIG_ARM_PL172_MPMC)	+= pl172.o
> +obj-$(CONFIG_APPLE_MCC)		+= apple-mcc.o
>  obj-$(CONFIG_ATMEL_SDRAMC)	+= atmel-sdramc.o
>  obj-$(CONFIG_ATMEL_EBI)		+= atmel-ebi.o
>  obj-$(CONFIG_BRCMSTB_DPFE)	+= brcmstb_dpfe.o
> diff --git a/drivers/memory/apple-mcc.c b/drivers/memory/apple-mcc.c
> new file mode 100644
> index 000000000000..55959f034b9a
> --- /dev/null
> +++ b/drivers/memory/apple-mcc.c
> @@ -0,0 +1,130 @@
> +// SPDX-License-Identifier: GPL-2.0-only OR MIT
> +/*
> + * Apple SoC MCC memory controller performance control driver
> + *
> + * Copyright The Asahi Linux Contributors

Copyright date?

> + */
> +
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_domain.h>
> +#include <linux/pm_opp.h>
> +
> +#define APPLE_MCC_PERF_CONFIG1  0xdc4
> +#define APPLE_MCC_PERF_CONFIG2  0xdbc
> +#define APPLE_MCC_CHANNEL(x)	((x) * 0x40000)
> +
> +struct apple_mcc {
> +	struct device *dev;
> +	struct generic_pm_domain genpd;
> +	void __iomem *reg_base;
> +	u32 num_channels;
> +};
> +
> +#define to_apple_mcc(_genpd) container_of(_genpd, struct apple_mcc, genpd)
> +
> +static int apple_mcc_set_performance_state(struct generic_pm_domain *genpd, unsigned int state)
> +{
> +	struct apple_mcc *mcc = to_apple_mcc(genpd);
> +	struct dev_pm_opp *opp;
> +	struct device_node *np;
> +	u32 perf_config[2];
> +	unsigned int i;
> +
> +	dev_dbg(mcc->dev, "switching to perf state %d\n", state);
> +
> +	opp = dev_pm_opp_find_level_exact(&mcc->genpd.dev, state);
> +	if (IS_ERR(opp))
> +		return PTR_ERR(opp);
> +
> +	np = dev_pm_opp_get_of_node(opp);
> +	if (of_property_read_u32_array(np, "apple,memory-perf-config",
> +		perf_config, ARRAY_SIZE(perf_config))) {
> +		dev_err(mcc->dev, "missing apple,memory-perf-config property");
> +		of_node_put(np);
> +		return -EINVAL;
> +	}
> +	of_node_put(np);
> +
> +	for (i = 0; i < mcc->num_channels; i++) {
> +		writel_relaxed(perf_config[0],
> +			       mcc->reg_base + APPLE_MCC_CHANNEL(i) + APPLE_MCC_PERF_CONFIG1);
> +		writel_relaxed(perf_config[1],
> +			       mcc->reg_base + APPLE_MCC_CHANNEL(i) + APPLE_MCC_PERF_CONFIG2);
> +	}
> +
> +	return 0;
> +}
> +
> +static unsigned int apple_mcc_opp_to_performance_state(struct generic_pm_domain *genpd,
> +						       struct dev_pm_opp *opp)
> +{
> +	return dev_pm_opp_get_level(opp);
> +}
> +
> +static int apple_mcc_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *node = dev->of_node;

By convention mostly we call the variable "np".

> +	struct apple_mcc *mcc;
> +	int ret;
> +
> +	mcc = devm_kzalloc(dev, sizeof(*mcc), GFP_KERNEL);
> +	if (!mcc)
> +		return -ENOMEM;
> +
> +	mcc->reg_base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(mcc->reg_base))
> +		return PTR_ERR(mcc->reg_base);
> +
> +	if (of_property_read_u32(node, "apple,num-channels", &mcc->num_channels)) {

Don't you have a limit of supported channels? It cannot be any uint32...

> +		dev_err(dev, "missing apple,num-channels property\n");

Use almost everywhere dev_err_probe - less code and you get error msg
printed.

> +		return -ENOENT;
> +	}
> +
> +	mcc->dev = dev;
> +	mcc->genpd.name = "apple-mcc-perf";
> +	mcc->genpd.opp_to_performance_state = apple_mcc_opp_to_performance_state;
> +	mcc->genpd.set_performance_state = apple_mcc_set_performance_state;
> +
> +	ret = pm_genpd_init(&mcc->genpd, NULL, false);
> +	if (ret < 0) {
> +		dev_err(dev, "pm_genpd_init failed\n");
> +		return ret;
> +	}
> +
> +	ret = of_genpd_add_provider_simple_noclk(node, &mcc->genpd);
> +	if (ret < 0) {
> +		dev_err(dev, "of_genpd_add_provider_simple failed\n");
> +		return ret;
> +	}
> +
> +	dev_info(dev, "Apple MCC performance driver initialized\n");

Please skip it, or at least make it a dev_dbg, you don't print any
valuable information here.

> +
> +	return 0;
> +}
> +
> +static const struct of_device_id apple_mcc_of_match[] = {
> +	{ .compatible = "apple,mcc" },
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(of, apple_mcc_of_match);
> +
> +static struct platform_driver apple_mcc_driver = {
> +	.probe = apple_mcc_probe,
> +	.driver = {
> +		.name = "apple-mcc",
> +		.of_match_table = apple_mcc_of_match,
> +	},
> +};

module_platform_driver() goes here.

> +
> +MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
> +MODULE_DESCRIPTION("MCC memory controller performance tuning driver for Apple SoCs");
> +MODULE_LICENSE("GPL v2");

I think this will be "Dual MIT/GPL", based on your SPDX.

> +
> +module_platform_driver(apple_mcc_driver);
> 


Best regards,
Krzysztof